This invention relates to an inkjet printing method. More particularly, this invention relates to an ink jet printing method using an ink jet recording element containing porous polymeric particles.
In a typical ink jet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye or pigment, and a large amount of solvent. The solvent, or carrier liquid, typically is made up of water, an organic material such as a monohydric alcohol, a polyhydric alcohol or mixtures thereof.
An ink jet recording element typically comprises a support having on at least one surface thereof an ink-receiving or image-forming layer, and includes those intended for reflection viewing, which have an opaque support, and those intended for viewing by transmitted light, which have a transparent support.
While a wide variety of different types of image-recording elements for use with ink jet devices have been proposed heretofore, there are many unsolved problems in the art and many deficiencies in the known products which have limited their commercial usefulness.
It is well known that in order to achieve and maintain photographic-quality images on such an image-recording element, an ink jet recording element must:
Be readily wetted so there is no puddling, i.e., coalescence of adjacent ink dots, which leads to non-uniform density
Exhibit no image bleeding
Absorb high concentrations of ink and dry quickly to avoid elements blocking together when stacked against subsequent prints or other surfaces
Exhibit no discontinuities or defects due to interactions between the support and/or layer(s), such as cracking, repellencies, comb lines and the like
Not allow unabsorbed dyes to aggregate at the free surface causing dye crystallization, which results in bloom or bronzing effects in the imaged areas
Have an optimized image fastness to avoid fade from contact with water or radiation by daylight, tungsten light, or fluorescent light
An ink jet recording element that simultaneously provides an almost instantaneous ink dry time and good image quality is desirable. However, given the wide range of ink compositions and ink volumes that a recording element needs to accommodate, these requirements of ink jet recording media are difficult to achieve simultaneously.
Inkjet recording elements are known that employ porous or non-porous single layer or multilayer coatings that act as suitable image-receiving layers on one or both sides of a porous or non-porous support. Recording elements that use non-porous coatings typically have good image quality but exhibit poor ink dry time. Recording elements that use porous coatings exhibit superior dry times, but typically have poorer image quality and are prone to cracking and flaking.
Japanese Kokai Hei 7[1995]-137433 relates to an ink jet recording paper containing polyester-based hollow porous resin particles containing cationic groups. However, it would be desirable to provide porous resin particles containing cationic groups which are not limited to polyester resins.
Japanese Kokai Hei 11[1999]-8569 relates to an ink jet recording sheet comprising porous organic particles which may be made cationic by adsorbing a cationic surfactant. However, there is a problem with these particles in that the cationic functionality is not part of the polymeric structure and is only adsorbed to the surface, not chemically bound, so that it could be desorbed from the particle surface during manufacture, storage or imaging.
It is an object of this invention to provide an ink jet printing method using an ink jet recording element that has a fast ink dry time. It is another object of this invention to provide an ink jet printing method using an ink jet recording element containing porous particles which have an ionic functionality which will bind ink jet inks thereto, thereby providing a porous receiver that has good water fastness. It is another object of this invention to provide an ink jet printing method using an ink jet recording element that has superior coating quality with acceptable cracking and flaking with low particle agglomeration.
These and other objects are achieved in accordance with the invention which comprises an ink jet printing method, comprising the steps of:
A) providing an ink jet printer that is responsive to digital data signals;
B) loading the printer with an inkjet recording element comprising a support having thereon an image-receiving layer comprising porous polymeric particles in a polymeric binder, the porous polymeric particles having the formula: 
wherein:
A represents units of an addition polymerizable monomer containing at least two ethylenically unsaturated groups;
B represents units of a copolymerizable, xcex1, xcex2-ethylenically unsaturated monomer;
C represents styrenic or acrylic repeating units containing an ionic functionality;
x is from about 27 to about 99 mole %;
y is from 0 to about 72 mole %; and
z is from about 1 to about 73 mole %;
C) loading the printer with an inkjet ink composition; and
D) printing on the image-receiving layer using the ink jet ink composition in response to the digital data signals.
By use of the invention, an ink jet printing method is obtained using an ink jet recording element which has better dry time, water fastness and coating quality (cracking and flaking) than prior art elements while providing good image quality.
In a preferred embodiment of the invention, x is from about 55 to about 99 mole %; y is from 0 to about 44 mole %; and z is from about 1 to about 45 mole %.
The support used in the inkjet recording element employed in the invention may be opaque, translucent or transparent. There may be used, for example, plain papers, resin-coated papers, plastics including a polyester resin such as poly(ethylene terephthalate), poly(ethylene naphthalate) and poly(ester diacetate), a polycarbonate resin, a fluorine resin such as poly(tetra-fluoro ethylene), metal foil, various glass materials, various voided or filled opaque plastics and the like. In a preferred embodiment, the support is paper or a voided plastic material. The thickness of the support employed in the invention can be from about 12 to about 500 xcexcm, preferably from about 75 to about 300 xcexcm.
The porous polymeric particles which are used in the invention are in the form of porous beads, porous irregularly shaped particles, or are aggregates of emulsion particles and contain an ionic functionality.
Suitable addition polymerizable monomers which can be used as Unit A above contain at least two ethylenically unsaturated groups, and may include, for example, the following monomers and their mixtures: esters of unsaturated monohydric alcohols with unsaturated monocarboxylic acids, such as allyl methacrylate, allyl acrylate, butenyl acrylate, undecenyl acrylate, undecenyl methacrylate, vinyl acrylate, and vinyl methacrylate; dienes such as butadiene and isoprene; esters of saturated glycols or diols with unsaturated monocarboxylic acids, such as, ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,3-butanediol dimethacrylate, pentaerythritol tetraacrylate, trimethylol propane trimethacrylate and polyfunctional aromatic compounds such as divinylbenzene divinylnaphthalene or derivatives thereof or other divinyl compound such as divinyl sulfide or divinyl sulfone compound, and the like. Preferably, A includes ethylene glycol dimethacrylate, ethylene glycol diacrylate, 1,4-butanediol dimethylacrylate or divinylbenzene. Most preferably, A is divinylbenzene or ethylene glycol dimethacrylate.
Suitable copolymerizable, xcex1, xcex2-ethylenically unsaturated monomers which can be used as Unit B above include, for example, the following monomers and their mixtures: acrylic monomers, such as acrylic acid, or methacrylic acid, and their alkyl esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, n-octyl acrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, nonyl acrylate, benzyl methacrylate; the hydroxyalkyl esters of the same acids, such as, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate; the nitriles and amides of the same acids, such as, acrylonitrile, methacrylonitrile, acrylamide, t-butylacrylamide and methacrylamide; vinyl compounds, such as, vinyl acetate, vinyl propionate, vinylidene chloride, vinyl chloride, and vinyl aromatic compounds such as styrene, t-butyl styrene, ethylvinylbenzene, chloromethylstyrene, vinyl toluene, styrene sulfonylchloride, vinylpyridine, and vinylimidazole; dialkyl esters, such as, dialkyl maleates, dialkyl itaconates, dialkyl methylene-malonates and the like. Preferably, B is styrene, vinyl toluene, ethylvinylbenzene, 2-hydroxyethyl methacrylate, chloromethylstyrene, methacrylic acid or methyl methacrylate.
The styrenic or acrylic repeating units of C above contain an ionic functionality which may be obtained using a preformed ionic monomer which carries a substantially permanent charge which survives the polymerization. Alternatively, functionalities in a formed porous polymeric particle can be modified to make them ionic. For example, pyridine can be protonated with an acid to form a quaternary nitrogen, an amine group can be quaternized with a chloroalkane, a carboxylic acid group can be neutralized with an amine or an alkali metal hydroxide to form a carboxylic anion, a chloromethyl group can be reacted with an amine to form a quaternary ammonium group, etc. Modifying functionalities in a formed porous polymeric particle is preferred.
Suitable copolymerizable, xcex1, xcex2-ethylenically unsaturated monomers containing a preformed ionic functionality which can be used as Unit C include, for example, the following monomers and their mixtures: cationic ethylenically unsaturated monomers, for example, vinylbenzyltrimethyl-ammonium chloride, vinylbenzyldimethyl-dodecylammonium chloride, other vinylbenzylammonium salts in which the three other ligands on the nitrogen can be any alkyl or carbocyclic group including cyclic amines such as piperidine, the counter ions of which can be halides, sulfonates, phosphates, sulfates, etc.; [2-(methacryloyloxy)ethyl]trimethyl-ammonium chloride, [2-(acryloyloxy)ethyl]-trimethylammonium p-toluene-sulfonate, and other acrylate and methacrylate ammonium salts in which the alkyl group connecting the acrylic function to the nitrogen can be xe2x89xa72 carbon atoms long and the other three nitrogen ligands can be any alkyl or carbocyclic group including cyclic amines such as piperidine, and benzyl; 4-vinyl-1-methylpyridinium methyl sulfate, 3-methyl-1-vinylimidazolium methosulfate, and other vinylpyridinium and vinylimidazolium salts in which the other nitrogen ligand is any alkyl or cycloalkyl group; vinyltriphenyl-phosphonium bromide, vinylbenzyltriphenylphosphonium tosylate, and other phosphonium salts in which the other three phosphorous ligands are any aromatic or alkyl group. In a preferred embodiment, the cationic functionality is vinylbenzyltrimethylammonium chloride, vinylbenzyl-N-butylimidazolium chloride, vinylbenzyldimethyldodecylammonium chloride or vinylbenzyl-dimethyloctadecylammonium chloride.
Other suitable copolymerizable, xcex1, xcex2-ethylenically unsaturated monomers containing a preformed ionic functionality which can be used as Unit C include, for example, the following monomers and their mixtures: anionic ethylenically unsaturated monomers such as 2-phosphatoethyl acrylate potassium salt, 3-phosphatopropyl methacrylate ammonium salt, and other acrylic and methacrylic esters of alkylphosphonates in which the alkyl group connecting the acrylic function to the phosphate function can be xe2x89xa72 carbon atoms long, the counter ions of which can be alkali metal cations, quaternary ammonium cations, phosphonium cations, or the like; sodium methacrylate, potassium acrylate, and other salts of carboxylic acids; styrenesulfonic acid ammonium salt, methyltriphenylphosphonium styrenesulfonate, and other styrene sulfonic acid salts; 2-sulfoethyl methacrylate pyridinium salt, 3-sulfopropyl acrylate lithium salt, and other acrylic and methacrylic esters of alkylsulfonates; and other sulfonates such as ethylene sulfonic acid sodium salt. In a preferred embodiment, the anionic functionality is trimethylammonium salt of methacrylic acid, dimethylbenzylammonium salt of methacrylic acid, dimethyldodecylammonium salt of methacrylic acid or methyltrioctylammonium salt of styrenesulfonic acid.
If the repeating Unit C is to be formed after the porous polymeric particle is prepared, all or some of Units A or Units B in a porous polymeric particle can be modified to make them (or part of them) ionic. All of the cationic and anionic functionalities mentioned above can be incorporated by modifying a non-ionic porous polymeric particle.
The porous polymeric particles used in this invention can be prepared, for example, by pulverizing and classification of porous organic compounds, by emulsion, suspension, and dispersion polymerization of organic monomers, by spray drying of a solution containing organic compounds, or by a polymer suspension technique which consists of dissolving an organic material in a water immiscible solvent, dispersing the solution as fine liquid droplets in aqueous solution, and removing the solvent by evaporation or other suitable techniques. The bulk, emulsion, dispersion, and suspension polymerization procedures are well known to those skilled in the polymer art and are taught in such textbooks as G. Odian in xe2x80x9cPrinciples of Polymerizationxe2x80x9d, 2nd Ed. Wiley (1981), and W. P. Sorenson and T. W. Campbell in xe2x80x9cPreparation Method of Polymer Chemistryxe2x80x9d, 2nd Ed, Wiley (1968).
Techniques to synthesize porous polymer particles are taught, for example, in U.S. Pat. Nos. 5,840,293; 5,993,805; 5,403,870; and 5,599,889, and Japanese Kokai Hei 5[1993]-222108, the disclosures of which are hereby incorporated by reference. For example, an inert fluid or porogen may be mixed with the monomers used in making the porous polymer particles. After polymerization is complete, the resulting polymeric particles are, at this point, substantially porous because the polymer has formed around the porogen thereby forming the pore network. This technique is described more fully in U.S. Pat. No. 5,840,293 referred to above.
A preferred method of preparing the porous polymeric particles used in this invention includes forming a suspension or dispersion of ethylenically unsaturated monomer droplets containing the crosslinking monomer A, the monomer containing an ionic functionality or a monomer containing a group which will be converted to an ionic functionality, and a porogen in an aqueous medium, polymerizing the monomer to form porous polymeric particles, and optionally removing the porogen by vacuum stripping. In a preferred embodiment of the invention, the particles thus prepared have a porosity as measured by a specific surface area of greater than 100 m2/g. The surface area is usually measured by B.E.T. nitrogen analysis known to those skilled in the art.
The porous polymeric particles used in the invention may be covered with a layer of colloidal inorganic particles as described in U.S. Pat. Nos. 5,288,598; 5,378,577; 5,563,226 and 5,750,378, the disclosures of which are incorporated herein by reference. The porous polymeric particles may also be covered with a layer of colloidal polymer latex particles as described in U.S. Pat. No. 5,279,934, the disclosure of which is incorporated herein by reference.
The porous polymeric particles used in this invention generally have a median diameter of from about 0.05 xcexcm to about 10 xcexcm, preferably from about 0.1 xcexcm to about 5 xcexcm. Median diameter is defmed as the statistical average of the measured particle size distribution on a volume basis. For further details concerning median diameter measurement, see T. Allen, xe2x80x9cParticle Size Measurementxe2x80x9d, 4th Ed., Chapman and Hall, (1990).
As noted above, the polymeric particles used in the invention are porous. By porous is meant particles which either have voids or are permeable to liquids. Preferred are particles which have voids. These particles can have either a smooth or a rough surface.
The polymeric binder used in the invention may comprise a poly(vinyl alcohol), a gelatin, a cellulose ether, polyvinylpyrrolidone, poly(ethylene oxide), etc. In a preferred embodiment of the invention, the ratio of the particles to the binder is from about 2:1 to about 15:1.
The image-receiving layer may also contain additives such as pH-modifiers like nitric acid, cross-linkers, rheology modifiers, surfactants, UV-absorbers, biocides, lubricants, water-dispersible latexes, mordants, dyes, optical brighteners etc.
The image-receiving layer may be applied to one or both substrate surfaces through conventional pre-metered or post-metered coating methods such as blade, air knife, rod, roll, slot die, curtain, slide, etc. The choice of coating process would be determined from the economics of the operation and in turn, would determine the formulation specifications such as coating solids, coating viscosity, and coating speed.
The image-receiving layer thickness may range from about 5 to about 100 xcexcm, preferably from about 10 to about 50 xcexcm. The coating thickness required is determined through the need for the coating to act as a sump for absorption of ink solvent.
Ink jet inks used to image the recording elements used in the present invention are well-known in the art. The ink compositions used in ink jet printing typically are liquid compositions comprising a solvent or carrier liquid, dyes or pigments, humectants, organic solvents, detergents, thickeners, preservatives, and the like. The solvent or carrier liquid can be solely water or can be water mixed with other water-miscible solvents such as polyhydric alcohols. Inks in which organic materials such as polyhydric alcohols are the predominant carrier or solvent liquid may also be used. Particularly useful are mixed solvents of water and polyhydric alcohols. The dyes used in such compositions are typically water-soluble direct or acid type dyes. Such liquid compositions have been described extensively in the prior art including, for example, U.S. Pat. Nos. 4,381,946; 4,239,543 and 4,781,758, the disclosures of which are hereby incorporated by reference.
The following examples further illustrate the invention.